Fission of charged nano-hydrated ammonia clusters-microscopic insights into the nucleation processes

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Abstract

While largely studied on the macroscopic scale, the dynamics leading to nucleation and fission processes in atmospheric aerosols are still poorly understood at the molecular level. Here, we present a joint experimental-theoretical study of a model system consisting of hydrogen-bonded ammonia and water molecules. Experimentally, the clusters were produced via adiabatic co-expansion. Double ionization ionic products were prepared using synchrotron radiation and analyzed with coincidence mass- and 3D momentum spectroscopy. Calculations were carried out using ab initio molecular dynamics to understand the fragmentation within the first ∼500 fs. Further exploration of the potential energy surfaces was performed at a DFT level of theory to gain information on the energetics of the processes. Water was identified as an efficient nano-droplet stabilizer, and is found to have a significant effect even at low water content. On the molecular level, the stabilizing role of water can be related to an increase in the dissociation energy between ammonia molecules and the water enriched environment at the cluster surface. Furthermore, our results support the role of ammonium as a charge carrier in the solution, preferentially bound to surrounding ammonia molecules, which can influence the atmospheric nucleation process.

Detaljer

Författare
Enheter & grupper
Externa organisationer
  • Autonomous University of Madrid
  • German Electron Synchrotron (DESY)
  • KTH Royal Institute of Technology
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Fysikalisk kemi
Originalspråkengelska
Sidor (från-till)25749-25762
Antal sidor14
TidskriftPhysical Chemistry Chemical Physics
Volym21
Utgåva nummer46
StatusPublished - 2019 dec 14
PublikationskategoriForskning
Peer review utfördJa